On The Face Of It: #2 Stick Built and Unitised Systems

The On The Face Of It blog series has been written to give property professionals an overview of the curtain wall facade, differences in system types and defects which are commonly observed during inspections.

Blog #2 in this series will look at two commonly used curtain wall types – Stick Built and Unitised Systems.

Stick Built Curtain Walls

The vast majority of stick built curtain walls use extruded aluminium to make the framing members. The main component parts of the framing are the vertical members (sticks) and transoms. All of the parts for the facade are manufactured in a factory and then shipped to site where they get assembled, piece by piece.

The mullions are installed first and are fixed to the floor slabs of the building. Once they are in place, the transoms are installed along with the infill panels which, in the 205 Queen Street example below, are all glass.

Gaskets are generally used to seal the perimeter of the infill units and external pressure plates hold the units in position.

With the exception of some ladder frame systems, assembly of the full stick built facade is undertaken on site.

Unitised Curtain Walls

The characteristics of a unitised system are similar to the stick system with the major difference being the use of pre-fabrication techniques. Unitised systems use factory assembled units that comprise of framing, fixings, infill panels, seals and gaskets. Units are lifted into position by cranes where they are aligned and fixed to brackets that are attached to the concrete floor slabs.

An example of a unitised system is PwC Tower on Quay Street, Auckland. This tower has more than one unitised system and the central vertical strip of flush glazing differs slightly in its construction to the remainder of the facades. You can find out more on the exact system types on the Thermosash website.

Unitised curtain wall systems are generally quicker to install than stick systems and they require a smaller site installation team. There are also far fewer site sealed joints with this system which means the risks associated with poor joint installation, and subsequent leaks, are greatly reduced.

The factory assembly of the units in these systems often produces a better quality facade that also allows the building to be enclosed quicker. However, framing for these systems is generally more complex and this comes with a price tag.

By Victoria Richardson

Further Examples of Stick Built and Unitised Facades:

Unitised: 21 Queen St, Auckland

Unitised: 23 Albert St, Wellington

Unitised: 157 Lambton Quay, Wellington

Stick: 45 Queen St, Auckland

Stick: 171 Featherston St, Wellington

Stick: 385 Queen St, Auckland

On The Face Of It Blog Series:

The next blog in this series will be published in March.

Blog #3 will look at the differences between pressure equalised and water managed facade systems.